In order to study the size dependency of grazing and growth rates in zooplankton, data were collected from laboratory studies in the literature, covering both limnic and marine organisms. Data were obtained from about 60 species of nano-, micro-, and mesozooplankton, representing flagellates, ciliates, rotifers, meroplankton larvae, copepods, and cladocerans. Estimates of maximum ingestion and clearance were extracted from functional responses (ingestion rates as a function of food density) established from laboratory experiments. Maximum specific rates were expressed as a function of predator body volume. Maximum specific clearance and ingestion rates decreased with predator volume within each group of zooplankton, with a common exponent (scaling factor) of -0.23 (SE = ±0.12)in accordance with previous findings. However, significant differences were found between groups. In particular, among the protists, ciliates display maximum ingestion, growth, and clearance rates that exceed those of dinoflagellates by a factor of 2-4. Among the metazooplankton, calanoid copepods have maximum clearance rates that exceed those of filter-feeding cladocerans and meroplankton larvae by a factor of 10. Because of these differences between the groups, the entire set of observations could not be fitted by an overall regression.